Algerian cities centers are composed of different types of structure such as unreinforced masonry (URM) buildings, reinforced concrete (RC) buildings, steel buildings and overall strengthened masonry buildings. This last is one of the most vulnerable buildings to earthquakes as it does not comply with the seismic code in practice. In this paper a contribution for safety assessment of overall strengthened masonry structures under seismic loading is developed. With this purpose, a vulnerability index method has been developed using numerical non-linear and empirical analyses and applied for overall strengthened masonry buildings, according to the Algerian seismic code (RPA). The first method uses a non-linear dynamic analysis by introducing ten seismic records for different buildings categories, and the second uses a database of 100 buildings located in Algiers. To do this the most important vulnerability parameters influencing the behavior of this kind of structures are identifying. Then three vulnerability classes (A, B and C) are proposed determining the state of each vulnerability parameter. Weighting factors are assigned to each parameter in order to calculate the vulnerability index and classified the investigated buildings according to a suggested classification. A comparison with two proposal classifications of overall strengthened masonry buildings is carried out, by applying to a certain number of structures according to the empirical and the numerical analyses.